export/hazard:

Added util function for organizing exported hazard curve results by
GMPE and IMT.
tests/export/hazard_test:

Added test for `_get_end_branch_export_path`.
tests/export/hazard_test:

Fixed a typo in test case class name
export/hazard:

Added missing argment in call to `_get_end_branch_export_path` in hazard
curve export function.
tests/export/hazard_test:

Added missing export test for disaggregation.
export/hazard:

Disagg results/exports are now organized into the same folder structure
as hazard curves.
Merge pull request #998 from larsbutler/haz-result-export-dir-structure

Hazard curve and disagg. result exports are now organized by GMPE and IMT

[r=micheles] [f=1097624]